Compressor employing piston-ring check valves

Abstract

A reciprocating compressor ( 26 ) includes two pistons ( 56 and 58 ) driven in opposite directions in a piston chamber ( 54 ). As a piston is driven in the downstream, compression-stroke direction, pressure causes a piston ring ( 64 or 66 ) that seals against the piston-chamber wall to seal against the piston, too, and thereby prevent fluid flow from the piston's downstream side to its upstream side. When the piston is driven downstream, on the other hand, pressure keeps the piston ring spaced from the piston and thereby allows flow from the piston's upstream side to its downstream side. The piston rings thus act as check valves.

What is claimed is:  
     
       1. A compressor that forms a compressor inlet and compressor outlet, draws fluid in through the compressor inlet, compresses fluid thereby drawn thereinto, drives the fluid thus compressed from the compressor outlet, and includes: 
       A) a piston-chamber wall that extends axially to define a piston chamber with which the compressor inlet and outlet communicate;  
       B) at least one piston disposed within the piston chamber and axially slidable with respect to the piston-chamber walls;  
       C) a piston driver that causes each piston to travel alternately in upstream and downstream directions; and  
       D) a piston ring associated with each piston, forming a sliding seal with the piston-chamber wall, and retained on that piston for limited axial movement with respect thereto between an upstream position, in which it so seals against the downstream face of the piston with which it is associated as to cooperate therewith to prevent fluid flow between the portions of the piston chamber upstream and downstream of the piston, and a downstream position, in which it is so spaced from the downstream face of the piston with which it is associated as to leave a fluid-flow path by which the portions of the piston upstream and downstream of the piston communicate, whereby the piston tends to move through the fluid in the piston chamber when the piston is moving upstream but tends to compress fluid in the portion of the piston chamber downstream thereof when the piston is moving downstream.  
     
     
       2. A compressor as defined in  claim 1  wherein each piston leaves between itself and the piston-chamber wall a clearance through which fluid can flow when the piston ring associated therewith is in its downstream position but not when it is in its upstream position. 
     
     
       3. A compressor as defined in  claim 2  wherein the area of the piston ring is at least one-quarter of that of the piston chamber's cross section. 
     
     
       4. A compressor as defined in  claim 1  wherein: 
       A) the compressor includes a plurality of said pistons; and  
       B) the piston driver drives each piston out of phase with at least one other said piston.  
     
     
       5. A compressor as defined in  claim 1  further including a stop associated with at least one said piston ring and disposed in a position so fixed with respect to the piston chamber as to prevent the piston ring with which that stop is associated from traveling upstream far enough to seal against the piston with which that piston ring is associated when that piston is at the upstream end of its travel. 
     
     
       6. A compressor as defined in  claim 1  further including at least one retainer associated with each piston, mounted thereon, and so positioned with respect thereto as to permit the relative motion of the piston ring associated therewith but to prevent relative downstream motion of that piston ring beyond its downstream position.